The present invention relates to a guide tube flow restrictor for use in conjunction with drive rod assemblies of a pressurized water nuclear reactor. The guide tube flow restrictor serves both to act as a guide for a drive shaft connected to a control rod and as a flow restrictor for primary coolant passing through the reactor.
In pressurized water nuclear reactors, the reactor head plenum contains a guide assembly for controlling the movement of various components such as control rods. Such an assembly generally contains a top support plate, having apertures therethrough, through which drive mechanisms for control rods pass. A guide assembly is provided that is disposed in the apertures to both guide the control rod drive shaft and control the upward flow of water through the apertures. Conventionally, such assemblies comprise a grommet-like member secured in the aperture by a plurality of flexure elements aligned in parallel relationship with he drive shaft, which flexure elements are mounted in special fittings supported in the top plate. Such conventional assemblies require machining and welding operations for installation of the flexure members and require time-consuming procedures for their replacement.
An improved type of assembly is described in copending application Ser. No. 574,839 filed Jan. 30, 1984 in the names of David E. Boyle and James R. Chrise, entitled "Quick Release Guide Sleeve Assembly", which application is assigned to the assignee of the present invention, the contents of said application incorporated herein by reference. In said application, the assembly comprises an outer sleeve, an inner sleeve, and a locking mechanism movably mounted on the outer sleeve for frictionally engaging the wall surfaces about an aperture in a top support plate of a guide tube rod assembly. The assembly described therein still, however, requires the use of a tool for assembly, as well as disassembly. Also, the construction is such that corrosion or accumulation of deposits about the locking mechanism could develop that would lead to difficulties in removal and replacement of such an assembly.
It is an object of the present invention to provide a guide tube flow restrictor that may be assembled without the need for special tools and is readily removable from its position in a support plate.
It is another object of the present invention to provide a guide tube flow restrictor that has a design that simplifies manufacture of such an assembly and is more economical.
It is a further object of the present invention to provide a guide tube flow restrictor that reduces the possibility of corrosion or collection of deposits between the assembly parts in use, such as would cause difficulties in removal or replacement of the assembly.